Electronic noise is one of the limiting factors in today's circuits. At least some of the electronic noise typically derives from back end digital signal processing, typically from the power supply and switching transistors. This electronic noise is deleterious to the performance of analog integrated circuits.
A device referred to as an opto-isolator (also referred to as an optical isolator, optocoupler and photocoupler) is often used to reduce noise in electrical circuits. Opto-isolators electrically isolate portions of a circuit thereby reducing noise. An opto-isolator uses a short optical transmission path to transfer a signal between elements of a circuit, typically a LED and a receiver, while keeping them electrically isolated. The LED and light sensor are separated so that light may travel across a barrier but electrical current may not. When an electrical signal is applied to the input of the opto-isolator, the LED generates a light signal, and a light detector generates a corresponding electrical signal as the output when the LED receives the light signal. When a photodiode is used as the light detector, the output current is proportional to the amount of incident light supplied by the LED. The ratio of the amount of current output by the photodiode to the amount of current input to the LED is referred to as the current transfer ratio.
Conventional embodiments utilizing LEDs have been limited, however, to low speed opto-isolation applications because they are limited by the response time of the LED. These conventional embodiments have also been limited in their current transfer ratio due to high power dissipation of LED emitters. The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate an example of technology areas where some embodiments may be practiced.